1. Field of the Invention
The present invention relates to the technical field of video transcoding and, more particularly, to a transcoder system for adaptively reducing frame rate.
2. Description of Related Art
For typically transmitting an audio-visual stream, due to the limitation of network bandwidth, the stream needs video transcoding to convert it into an audio-visual stream with reduced frame-rate for transmission in a congested network. Namely, in video transcoding, frame-rate for moving picture compression data is reduced to form another moving picture compression data that reduces frame-rate and further bit-rate for meeting insufficient video transmission requirement.
FIG. 1 is a block diagram of a typical video transcoder. As shown, a decoder 110 decodes a moving picture compression data and eliminates unwanted pictures. Next, an encoder 120 re-compresses and re-codes the remaining pictures in order to obtain reduced frame-rate. However, such a processing consumes much time because a motion vector estimation step is a must for coding.
To overcome this, a solution proposed that motion vectors for macroblocks originally inputted are applied repeatedly to video transcoding. FIG. 2 is a block diagram of a typical video transcoder applied for the aforementioned solution. As shown in FIG. 2, a variable length decoder is applied to compute the motion vectors of the macroblocks and next store the motion vectors in a memory used by a motion vector compensator in coding. However, only I- and P-pictures are transcoded for reduced frame-rate in the prior art, which skips B-pictures and thus cannot perform video transcoding completely and quickly for reduced frame-rate.
Therefore, it is desirable to provide an improved transcoder system to mitigate and/or obviate the aforementioned problems.